The present invention relates to of the art of manufacturing chairs and, more particularly, to a novel pivot assembly for swiveling chairs. The pivot assembly is characterized by its ability to maintain tight tolerances between its component parts during its useful life to prevent undesirable free play felt by the occupant of the chair when the latter shifts the position of his body while being seated.
A typical swiveling chair includes a body supporting structure that is mounted on a chair base by a pivot assembly. Many different pivot assembly arrangements have been developed in the past to suit a wide variety of applications. One type of pivot assembly that is fairly common comprises an elongated rod that extends generally upright, depending from the body supporting structure. The elongated rod is received in a tubular element that is secured to the chair base. Bearings between the elongated rod and the tubular element allow the swiveling motions to take place. Normally, two separate bearing assemblies are used to connect the elongated rod to the tubular element. The two bearing assemblies are mounted in spaced apart relationship on the elongated rod.
It is well known that overtime the clearances between the various components of the pivot assembly will progressively increase. This occurs as a result of normal wear. This increase in clearances will result in an undesirable free play in the pivot assembly that can be distinctly felt by the user, particularly as a result of body shifts. For example, when the body of the user leans forward or leans backwards the center of gravity crosses the imaginary vertical plane containing the swiveling axis and makes this free play particularly noticeable.
To overcome, this problem, it is known to provide the pivot assembly with an adjustable cushion designed to reduce the undesirable free play. This adjustable cushion is in the form of a polymeric sleeve that is placed within the tubular element and surrounds the elongated rod. Adjustment screws are placed on the tubular element to urge the polymeric sleeve towards the elongated rod such as to eliminate the free play. The difficulty of this approach is the requirement from the user to make periodic adjustments. Also, once an adjustment has been made the polymeric sleeve will be able to eliminate or reduce the free play usually over a fairly short period of time, such as a couple of weeks. After this period of time has elapsed, the free play will progressively reappear and the user will be required to perform the adjustment again.
Against this background, it clearly appears that there is a need in the industry to provide a pivot assembly that has the ability to maintain tight tolerances between its component parts over long time periods and that does not require frequent periodic adjustments.
In one aspect the present invention provides a pivot assembly for a swiveling chair, the pivot assembly being suitable for supporting a body supporting structure of the chair on a chair base and allow the body supporting structure to swivel with relation to the chair base. The pivot assembly comprises a first pivot assembly component for connection to the body supporting structure and a second pivot assembly component for connection to the chair base. One of the first and second pivot assembly components including an elongated rod oriented generally upright.
A bearing assembly is mounted between the first and the second pivot assembly components to allow the pivot assembly components to swivel one with relation to the other. The bearing assembly defines an aperture that receives the elongated rod. The bearing assembly is responsive to pressure applied downwardly on the pivot assembly to tend to close the aperture on the elongated rod.
The downward pressure applied on the bearing assembly can originate from different sources. In one possible nonlimiting example of implementation, the downward pressure is a combination of two factors, the first factor being the weight of the body of the occupant when seated in the body supporting structure, while the second factor is a resilient element that urges the pivot assembly downwards. It should be appreciated that in this specific nonlimiting example of implementation, the resilient element is optional and it can be omitted without departing from the spirit of the invention. Under a possible variant where no resilient element is present, the pivot assembly relies solely on the weight of the body of the occupant to generate the downward pressure necessary to tend to close the aperture in the bearing assembly around the elongated rod. Yet, another possibility is to provide a large resilient element that alone, without relying on the body weight of the occupant, could generate the downward pressure sufficient to tend to close the aperture of the bearing assembly on the elongated rod in a manner to reduce or eliminate clearances.
Having regards to the above, it should be appreciated that the expression xe2x80x9cdownwards pressurexe2x80x9d in this specification is not limited to any particular external influence or a combination of external influences that generate the downward pressure acting on the pivot assembly. The expression xe2x80x9cdownward pressurexe2x80x9d is intended to encompass all possible sources or combination of such sources of downward force acting on the pivot assembly as long as the resulting magnitude is sufficient to tend to close the aperture of the bearing assembly on the elongated rod.
The advantage of this pivot assembly in accordance with this invention is its ability to maintain tight tolerances primary between the elongated rod and the bearing assembly. As a result, less frequent adjustments are necessary to compensate for free play by comparison to prior art devices.
In a specific nonlimiting example of implementation, the first pivot assembly component is the elongated rod while the second pivot assembly component is a tubular element that receives the elongated rod. The bearing assembly includes a first segment and a second segment concentrically mounted on the elongated rod. The first segment of the bearing assembly includes a downward tapering recess formed on the second segment. The first segment includes a slot that extends along the elongated rod. Functionally, under this nonlimiting example of implementation, the first segment behaves as a slotted ring and it can be progressively tightened on the elongated rod in response to radial force applied on the first segment. This radial force is generated as a result of the tapering configuration of the mating surfaces of the first and of the second segments, when downward pressure is applied on the pivot assembly. implementation, the pivot assembly includes a second bearing assembly that is mounted on the elongated rod and it is in a spaced apart relationship with relation to the first bearing assembly. The second bearing assembly functions in a similar manner as the first bearing assembly with one notable exception. This exception is that the mating surfaces between the first and the second segments of the second bearing assembly are oriented in such a way that they taper upwardly, in other words opposite the direction of taper of the mating surfaces of the first and the second segments of the first bearing assembly.
Under a different aspect, the present invention provides a pivot assembly for a swiveling chair, the pivot assembly being suitable for supporting a body supporting structure of the chair on a chair base and allowing the body supporting structure to swivel with relation to the chair base. The pivot assembly comprises a first pivot assembly component for connection to the body supporting structure and a second pivot assembly component for connection to the chair base. One of the first and second pivot assembly components includes an elongated rod oriented generally upright. A bearing assembly is mounted between the first and second pivot assembly components to allow the pivot assembly components to swivel one with relation to the other. The bearing assembly defines an aperture that receives the elongated rod. The bearing assembly includes a first segment and a second segment that are mechanically engaged and operative to pivot one with relation to another when the pivot assembly swivels. The bearing assembly is responsive to pressure urging the segments toward one another to tend to close the aperture on the elongated rod.
The pressure urging the segments of the bearing assembly toward one another can come from one or more sources, such as the body weight of the occupant of the chair and/or a resilient element in the pivot assembly operative to urge the segments toward one another.
The present invention also extends to a swiveling chair including the pivot assembly described above.
In a different aspect the invention provides a pivot assembly for a swiveling chair, the pivot assembly being suitable for supporting the body supporting structure of the chair on a chair base and allowing the body supporting structure to swivel with relation to the chair base. The pivot assembly comprises a first pivot assembly component for connection to the body supporting structure and a second pivot assembly component for connection to the chair base, one of the first and second pivot assembly components including an elongated rod oriented generally upright. A bearing assembly is mounted between the first and the second pivot assembly components. The bearing assembly allows the pivot assembly components to swivel one relative to the other. The bearing assembly includes a first segment and a second segments, the first segment including a tapered projection and being concentrically mounted on the elongated rod. The first segment is secured on the elongated rod against movement on the elongated rod along a direction parallel to the elongated rod and a direction transverse to the elongated rod. The second segment includes a tapered recess receiving the tapered projection. The first and second segments are in mechanical engagement and operative to pivot one with relation to the other when the pivot assembly swivels.